I just recently put my plants outside because my indoor area was getting overcrowded...not sure why I didn't think of it sooner...several of them are already definitely in "YAY!!" mode since being put out! Not sure if it's the humid air, the breeze, the rainwater, the temperature differentials, or all of it...but I would say they definitely KNOW they're outdoors.
Now I wish I had put them out back in June...I would probably have some sun-lovers in bloom right now if I had. Oh well...I'll at least make the most of whatever warm weather we have left, and next year they'll definitely be going out earlier! (Well, all except my large phal collection, that is...the phals are SO happy indoors that I don't want to mess with a system that's been working perfectly! LOL)